[Closed] Which Rockshox Damper?

I've been looking for a new 29er fork for the bike and have pretty much decided on a Rockshox SID, mainly because the Lefty forks are just a bit too expensive!

Having looked at the SID's, I've narrowed it down to either the XX or the RCT3 but after reading bits about them I'm still none the wiser as to which I should get.

Can anyone tell me what the main differences are and which would be better for a singlespeed 29er riding general XC stuff?
I'd prefer a fork with tapered steerer and 15mm axle if that makes any difference.